The world’s oceans play a huge role in absorbing carbon dioxide from the atmosphere, especially as human emissions of the greenhouse gas continue to rise. But that service comes at a price: The oceans are projected to become more acidic over the next century.

As CO2 dissolves in the water, it lowers the pH, which shrinks the pool of carbonate ions in the ocean that marine organisms such as crabs and corals use to build skeletons and shells. The physiology of other marine species may also be affected. There is growing evidence that the oceans are acidifying more rapidly and at a pace unprecedented in hundreds of millions of years.

The cold polar oceans would be the first to acidify because they are already undersaturated with carbonate ions. Three projects funded by the National Science Foundation are studying this problem in different ways: